Nares-to-carina distance in children: does a 'modified Morgan formula' give useful guidance during nasal intubation?

Simulated dimensional compatibility of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children

BACKGROUND

Cuffed tracheal tubes have recently been recommended for selective endobronchial intubation to establish single-lung ventilation even in smaller children. This implies that, compared with uncuffed tracheal tubes, the cuffed tracheal tubes selected will be smaller and therefore have a shorter length. We hypothesized that cuffed tracheal tubes might be of insufficient length for selective endobronchial intubation if the tube cuff were fully immersed in the left or right mainstem bronchus.

METHODS

The distance from the proximal end of the tracheal tube to the upper border of the cuff in cuffed tracheal tubes and to the upper margin of the Murphy eye in uncuffed tracheal tubes, respectively, was assessed in sizes 3.0-7.0 mm internal diameter. The raw data sets of two previously performed studies obtained from 337 children aged from birth to 16 years, including the distances "teeth to tracheal tube tip" and "tracheal tube tip to carina," were used to calculate age-, weight-, and height-related data for the distance from "teeth to carina." Tracheal tube dimensions were compared with age-related distances from "teeth to carina," applying published recommendations for the selection of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children.

RESULTS

The differences between the length of the age-related tracheal tube and the tracheal tube insertion length required to guarantee full insertion of the tracheal tube cuff or the Murphy eye within the mainstem bronchus ranged from -3.5 to 52.6 mm in cuffed tracheal tubes and from 42.3 to 83.3 mm in uncuffed tracheal tubes.

CONCLUSIONS

For many age groups of patients requiring selective endobronchial intubation, the lengths of cuffed tracheal tubes, in contrast to those of uncuffed tracheal tubes, were revealed to be critically short for safe taping outside the oral cavity with the cuff placed completely within the right or left mainstem bronchus.

Longer upper airway lengths in Robin Sequence: A case-control study using computed tomography

BACKGROUND

Direct laryngoscopy and intubation are often difficult in children with Robin Sequence. Previous research characterizing anatomic airway differences has focused on parameters influencing airway patency; there is a paucity of data pertaining to intubation trajectories and depth. Such information could impact airway management approaches and decrease the incidence of endotracheal tube malpositioning.

AIM

The study goal was to examine whether longitudinal airway parameters pertaining to intubation are different in children with Robin Sequence compared with age-matched controls.

METHOD

This case-control study compared patients with RS <4 years of age who had computed tomography scans of the head and neck to age- and sex-matched controls. Measurements were made of the nasopharynx, oropharynx, hypopharynx, tongue, hyoid, and the front teeth to vocal cord, nares to vocal cord, and nasion-basion distances. Statistical analysis was performed using multiple ANCOVA models with the categorical predictor of Robin Sequence vs control and potential covariates including subject height/length, weight, and age.

RESULTS

Thirty-three patients with Robin Sequence and 33 control subjects were included. After controlling for subject height/length, mean front teeth to vocal cord distance was 1.2 cm longer (95% CI: 0.9 to 1.6 cm, P < .001) and mean nares to vocal cord distance was 0.8 cm longer (95% CI: 0.4 to 1.2 cm, P < .001) in patients with Robin Sequence than in controls. The tongue was positioned on average 0.5 cm higher (95% CI: 0.3 to 0.8, P < .001) and 0.9 cm more posterior (95% CI: 0.6 to 1.0 cm, P < .001) in cases than in controls. Moreover, in patients with Robin Sequence, the hyoid was positioned on average 0.5 cm more inferiorly (95% CI: 0.2 to 0.8 cm, P < .001) and 0.2 cm more posteriorly (95% CI: 0.1 to 0.4 cm, P < .01) than controls.

CONCLUSION

In patients with Robin Sequence under 4 years of age, the mean front teeth to vocal cord distance was found to be 1.2 cm longer while the mean nares to vocal cord distance was found to be 0.8 cm longer controlling for subject length. Clinicians should account for these differences when selecting and placing endotracheal tubes, particularly those with a preformed bend.

Nasolaryngeal Distances in the Adult Population and an Evaluation of Commercially Available Nasotracheal Tubes

BACKGROUND

Preformed nasal endotracheal tubes (NETs) come with a predefined insertion depth due to their curved design. While size indication refers to internal diameter, there is a considerable variability in the corresponding lengths and proportions of same-sized tubes of different manufacturers which is probably based on the lack of data of nasolaryngeal distances (NLDs) in the adult population. Choosing the best-fitting NET is therefore difficult and carries the risk of endobronchial intubation or, on the contrary, cuff inflation at the vocal cord level. The aim of this study was to develop a prediction model for NLD and a selection guide to choose the appropriate NET based on a radiographic description of NLD in comparison to the measurements of available NETs of several manufacturers.

METHODS

After institutional ethics board review, 388 computed tomography (CT) scan images of head, neck, and upper thorax in a heterogeneous adult cohort were included. Mean distances from the nares to the lower border of the thyroid cartilage were measured. NETs from different manufacturers were measured and compared to the NLD derived from the radiographic analysis. The patients' sex, body height, and weight were considered as possible covariates in quantile regression models for predicting the NLD.

RESULTS

Data from 200 patients were analyzed. NLD was associated with sex, body height, and weight. A simple quantile regression model using the body height as the only covariate sufficed to achieve accurate predictions of NLD. Validation on independent test data showed that 92.8% of the NLD predictions were closer than ±20 mm to the observed NLD values. Measurements of equal-sized NETs varied considerably in outer diameter, proportion, the nasopharyngeal part, and guide marks. Length differences of the bend-to-cuff distance, containing the anatomically NLD, ranged between 218 and 270 mm at same sizes.

CONCLUSIONS

A reliable prediction of NLD can be obtained simply by body height, using the formula (Equation is included in full-text article.). As manufacturers' tube lengths vary substantially, additional information about the bend-to-cuff distance as corresponding tube section would allow for more accurate tube selection.

Shallow nasal RAE tube depth after head and neck surgery: association with preoperative and intraoperative factors

PURPOSE

To evaluate risk factors associated with improper postoperative nasal Ring-Adair-Elwyn (RAE) tube depth.

METHODS

We retrospectively enrolled 133 adult patients who were admitted to the intensive care unit (ICU) with the nasal RAE tube after head and neck surgery. Postoperative chest radiography was performed to confirm nasal RAE tube depth immediately after the patient was admitted to the ICU. Proper tube depth was defined as the tube tip between 2 and 7 cm above the carina. The patients were divided into the proper-depth group (78 patients) and the improper-depth group (55 patients). Patients' characteristics were collected. The risk factors for improper postoperative tube depth were assessed using logistic regression analysis.

MAIN RESULTS

All patients who showed improper tube depth had a shallow tube depth (the tube tip > 7 cm above the carina). Multivariable analysis revealed that tall stature [odds ratio (OR) 1.16; 95% confidence interval (CI) 1.08-1.25; P < 0.001], prolonged anesthesia duration (OR 1.16; 95% CI 1.02-1.32; P = 0.026), and right-sided surgical field as compared to the left (OR 0.36; 95% CI 0.14-0.93; P = 0.034) or median field (OR 0.25; 95% CI 0.07-0.85; P = 0.027) were risk factors associated with postoperative shallow tube depth.

CONCLUSIONS

Tall stature, prolonged anesthesia duration, and right-sided surgical field were independent risk factors for postoperative shallow nasal RAE tube depth.

Changes in nasotracheal tube depth in response to head and neck movement in children

BACKGROUND

A tracheal tube is often inserted via the nasal cavity for dental surgery. The position of the tube tip is important, given that the head position sometimes changes during surgery. Head movement induces changes in the length of the trachea (t-length) and/or the distance between the nare and the vocal cords (n-v-distance). In this study, we investigated the changes in t-length and n-v-distance in children undergoing nasotracheal intubation.

METHODS

Eighty patients aged 2-8 year undergoing dental surgery were enrolled. After nasotracheal intubation with an uncuffed nasotracheal tube (4.5-6.0 mm), the tube was fixed at the patient's nares. The distance between the tube tip and the first carina was measured using a fibrescope with the angle between the Frankfort plane and horizontal plane set at 110°. The location of the tube in relation to the vocal cords was then checked. These measurements were repeated at angles of 80° (flexion) and 130° (extension). The t-length and n-v-distance were then calculated using these measurements.

RESULTS

On flexion, the t-length shortened significantly from 87.5 ± 10.4 mm to 82.9 ± 10.7 mm (P = 0.017) and the n-v-distance decreased from 128.1 ± 10.7 mm to 125.6 ± 10.4 mm (P = 0.294). On extension, the t-length increased significantly from 87.5 ± 10.4 mm to 92.7 ± 10.1 mm (P = 0.007) and the n-v-distance increased from 128.1 ± 10.7 mm to 129.4 ± 10.7 mm (P = 0.729). The change in t-length was significantly greater than that in the n-v-distance.

CONCLUSION

A change in the position of the tracheal tube tip in the trachea depends mainly on changes in t-length during paediatric dental surgery.

Airway Management for a Pediatric Patient With a Tracheal Bronchus

Tracheal bronchus is an ectopic bronchus almost arising from the right side of the tracheal wall above the carina. The incidence of a tracheal bronchus is reported as 0.1 to 3%. We experienced a patient with tracheal bronchus that was incidentally found at induction of anesthesia. Endotracheal intubation in a patient with tracheal bronchus might cause obstruction of the tracheal bronchus, although in this case, ventilation was not impaired.